This level is entirely set underground. There is a box next to you. Stomp it to get some crystals. Then there is a movable crate. You can use it to reach a suspended platform on which the green crystal is located (kill the Dantini that flutters nearby if it bothers you). Then push the crate along the path and use it to climb on the monkey bars, where you will find the red crystal and a button. By pressing it, you will drop a platform, above the lava pool. Reach it quickly and climb on it. You can then reach the first Gobbo, on a ledge. After getting it, go back down and enter the door.
Grab the balloon to go downstairs while collecting the crystals. You will land on a collapsing platform, on which the blue crystal is located. Quickly jump to avoid falling into the lava and climb onto the double arrow platform. Use it to cross the lava pool, killing the flying Dantini with a swipe of the tail if they get close. On the other side you will find a chest with the second Gobbo. Then enter the door a little further on.
Reach the islet in the middle of the lava pool using the platform. Collect the crystals, avoiding the flames that cross the islet. Both to the right and to the left there is a chest, which you can reach by jumping on the precarious platforms. In the one on the right you will find the yellow crystal and in the one on the left the third Gobbo. Then pass the pool using the rotating platform. You will come to a well from which a pink snake leaps out. When the snake retreats, collect the crystals around the well and enter the door.
On the right, behind the gong, you will find the pink crystal. Then cross the precarious bridge on the left and further on, on the right, you will find a chasm, with a multi-arrow platform. Use the platform to collect the crystals suspended above the chasm and reach the other side. You will find a chest with a silver key on it. Break the chest to find the fourth Gobbo. Then go back and open the cage above the lava pool that you have certainly noticed, to free the fifth Gobbo. Cross the precarious bridge again and enter the crystal door on the left.
In front of you you will see a staircase made of crates. Climb high, without breaking them. At the top, there are three boxes suspended one above the other. Climb on top and let yourself fall on the other side, staying close to the crates. As you fall, you will get a silver key. Thanks to it, you can open the cage where the sixth Gobbo is located, just below. Then proceed to break all the other crates in the usual way, to get a good amount of crystals. Finally, hit the gong to complete the level.